U.S. patent number 6,534,692 [Application Number 09/816,509] was granted by the patent office on 2003-03-18 for methanol to olefin process with increased selectivity to ethylene and propylene.
This patent grant is currently assigned to UOP LLC. Invention is credited to Paul T. Barger, Bipin V. Vora.
United States Patent |
6,534,692 |
Barger , et al. |
March 18, 2003 |
Methanol to olefin process with increased selectivity to ethylene
and propylene
Abstract
A process for converting methanol to light olefins is disclosed
and claimed. The catalyst is a metalloaluminophosphate molecular
sieve having the empirical formula (E.sub.x Al.sub.y
P.sub.z)O.sub.2 where EL is a metal such as silicon or magnesium
and "x", "y" and "z" are the mole fractions of EL, Al and P
respectively and specifically where "x" has a value of about 0.02
to about 0.08. A preferred molecular sieve is one which has
predominantly a plate crystal morphology in which the average
smallest crystal dimension is at least 0.1 microns and has an
aspect ratio of no greater than 5. The process provides greater
selectivity to ethylene and propylene versus C.sub.4+
byproducts.
Inventors: |
Barger; Paul T. (Arlington
Heights, IL), Vora; Bipin V. (Naperville, IL) |
Assignee: |
UOP LLC (Des Plaines,
IL)
|
Family
ID: |
46279927 |
Appl.
No.: |
09/816,509 |
Filed: |
March 23, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
305960 |
May 6, 1999 |
6207872 |
|
|
|
987085 |
Dec 9, 1997 |
5912393 |
|
|
|
Current U.S.
Class: |
585/640;
585/639 |
Current CPC
Class: |
B01J
37/0009 (20130101); C07C 1/20 (20130101); B01J
29/85 (20130101); C07C 1/20 (20130101); C07C
11/02 (20130101); Y02P 30/40 (20151101); B01J
2229/26 (20130101); Y02P 30/20 (20151101); Y02P
30/42 (20151101); B01J 2229/42 (20130101); Y02P
20/52 (20151101); C07C 2529/85 (20130101) |
Current International
Class: |
B01J
29/00 (20060101); B01J 29/85 (20060101); C07C
1/00 (20060101); B01J 37/00 (20060101); C07C
1/20 (20060101); C07C 001/00 () |
Field of
Search: |
;585/639,640,642 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Dunn; Tom
Assistant Examiner: Ildebrando; Christina
Attorney, Agent or Firm: Tolomei; John G. Molinaro; Frank
S.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of U.S. application Ser.
No. 09/305,960, filed May 6, 1999 and issued as U.S. Pat. No.
6,207,872 B1 which in turn is a continuation-in-part of U.S.
application Ser. No. 08/987,085 filed Dec. 9, 1997, now U.S. Pat.
No. 5,912,393 B1 all of which are incorporated by reference.
Claims
What is claimed is:
1. A process for converting methanol to light olefins comprising
contacting the methanol with a catalyst at conversion conditions to
provide the olefins, the catalyst comprising a crystalline metallo
aluminophosphate molecular sieve having a chemical composition on
an anhydrous basis expressed by an empirical formula of:
where EL is a metal selected from the group consisting of silicon,
magnesium, zinc, iron, cobalt, nickel, manganese, chromium and
mixtures thereof, "x" is the mole fraction of EL and has a value of
about 0.02 to about 0.08, "y" is the mole fraction of Al and has a
value of at least 0.01, "z" is the mole fraction of P and has a
value of at least 0.01 and x+y+z=1, the molecular sieve
characterized in that it has predominantly a plate crystal
morphology, wherein the average smallest crystal dimension is at
least 0.1 micron and has an aspect ratio of less than or equal to
5.
2. The process of claim 1 where the EL metal is selected from the
group consisting of silicon, magnesium, cobalt and mixtures
thereof.
3. The process of claim 2 where EL is silicon.
4. The process of claim 3 where the silicon aluminophosphate has
the crystal structure of SAPO-34.
5. The process of claim 1 where "x" has a value of about 0.02 to
about 0.07.
6. The process of claim 1 where "x" has a value of about 0.03 to
about 0.068.
7. The process of claim 1 where the catalyst comprises a
metallo-alumino-phosphate molecular sieve and an inorganic oxide
binder.
8. The process of claim 7 where the binder is selected from the
group consisting of alumina, silica, aluminum phosphate,
silica-alumina and mixtures thereof.
9. The process of claim 7 where the molecular sieve is present in
an amount from about 10 to about 90 weight percent of the
catalyst.
10. The process of claim 7 where the molecular sieve is present in
an amount from about 30 to about 70 weight percent of the
catalyst.
11. The process of claim 1 where the conversion conditions are a
temperature of about 300.degree. C. to about 600.degree. C., a
pressure of about 0 kPa to about 17224 kPa (250 psig) and a weight
hourly space velocity of about 1 to about 100 hr.sup.-1.
12. The process of claim 1 where the average smallest crystal
dimension is at least 0.2 microns.
13. The process of claim 1 where the aspect ratio is less than or
equal to 2 and the crystal morphology is cubic.
14. A process for converting methanol to light olefins comprising
contacting the methanol with a catalyst at conversion conditions to
provide the olefins, the catalyst comprising a crystalline silico
aluminophosphate molecular sieve having a chemical composition on
an anhydrous basis expressed by an empirical formula of:
where "x" is the mole fraction of Si and has a value of about 0.02
to about 0.08, "y" is the mole fraction of Al and has a value of at
least 0.01, "z" is the mole fraction of P and has a value of at
least 0.01 and x+y+z=1, the molecular sieve characterized in that
it has predominantly a plate crystal morphology, wherein the
average smallest crystal dimension is at least 0.1 micron and has
an aspect ratio of less than or equal to 5 and the conversion
conditions comprise a temperature of about 300.degree. C. to about
600.degree. C., a pressure of about 0 kPa to about 17224 kPa (250
psig) and a weight hourly space velocity of about 1 to about 100
hr.sup.-1.
15. The process of claim 14 where the catalyst comprises
silico-aluminophosphate molecular sieve and an inorganic oxide
binder.
16. The process of claim 15 where the binder is selected from the
group consisting of alumina, silica, aluminum phosphate,
silica-alumina and mixtures thereof.
17. The process of claim 15 where the molecular sieve is present in
an amount from about 10 to about 90 weight percent of the
catalyst.
18. The process of claim 15 where the molecular sieve is present in
an amount from 30 to about 70 weight percent of the catalyst.
19. The process of claim 14 where the average smallest crystal
dimension is at least 0.2 microns.
20. The process of claim 14 where the aspect ratio is less than or
equal to 2 and the crystal morphology is cubic.
21. The process of claim 14 where "x" has a value of about 0.02 to
about 0.07.
22. The process of claim 14 where "x" has a value of about 0.03 to
about 0.068.
23. The process of claim 14 where the silicon aluminophosphate has
the crystal structure of SAPO-34.
Description
FIELD OF THE INVENTION
This invention relates to a process for converting methanol to
light olefins with increased selectivity to ethylene and propylene.
The process comprises contacting the methanol with a catalyst
comprising a metallo aluminophosphate molecular sieve having an
empirical formula of (EL.sub.x Al.sub.y P.sub.z)O.sub.2 where EL
includes silicon and characterized in that "x" has a value from
about 0.02 to about 0.08. A preferred catalyst is one where the
molecular sieve has predominantly a plate crystal morphology such
that the average smallest crystal dimension is at least 0.1 micron
and has an aspect ratio of less than or equal to 5.
BACKGROUND OF THE INVENTION
The limited supply and increasing cost of crude oil has prompted
the search for alternative processes for producing hydrocarbon
products. One such process is the conversion of methanol to
hydrocarbons and especially light olefins (by light olefins is
meant C.sub.2 to C.sub.4 olefins). The interest in the methanol to
olefin (MTO) process is based on the fact that methanol can be
obtained from coal or natural gas by the production of synthesis
gas which is then processed to produce methanol.
Processes for converting methanol to light olefins are well known
in the art. Initially aluminosilicates or zeolites were used as the
catalysts necessary to carry out the conversion. For example, see
U.S. Pat. No. 4,238,631 B1; U.S. Pat. No. 4,328,384 B1, U.S. Pat.
No. 4,423,274 B1. These patents further disclose the deposition of
coke onto the zeolites in order to increase selectivity to light
olefins and minimize the formation of C.sub.5+ byproducts. The
effect of the coke is to reduce the pore diameter of the
zeolite.
The prior art also discloses that silico aluminophosphates (SAPOs)
can be used to catalyze the methanol to olefin process. Thus, U.S.
Pat. No. 4,499,327 B1 discloses that many of the SAPO family of
molecular sieves can be used to convert methanol to olefins. The
'327 patent also discloses that preferred SAPOs are those that have
pores large enough to adsorb xenon (kinetic diameter of 4.0 .ANG.)
but small enough to exclude isobutane (kinetic diameter of 5.0
.ANG.). A particularly preferred SAPO is SAPO-34.
U.S. Pat. No. 4,752,651 B1 discloses the use of nonzeolitic
molecular sieves (NZMS) including ELAPOs and MeAPO molecular sieves
to catalyze the methanol to olefin reaction.
The effect of the particle size of the molecular sieve on activity
has also been documented in U.S. Pat. No. 5,126,308 B 1. In the
'308 patent it is disclosed that molecular sieves in which 50% of
the molecular sieve particles have a particle size less than 1.0
.mu.m and no more than 10% of the particles have a particle size
greater than 2.0 .mu.m have increased activity and/or durability.
The '308 patent also discloses that restricting the silicon content
to about 0.005 to about 0.05 mole fraction also improves catalyst
life by reducing coke formation.
In contrast to this art, applicants have found that a methanol to
olefin process using molecular sieves having the empirical formula
(EL.sub.x Al.sub.y P.sub.z)O.sub.2 (hereinafter ELAPO) where EL is
a metal selected from the group consisting of silicon, magnesium,
zinc, iron, cobalt, nickel, manganese, chromium and mixtures
thereof and "x", "y" and "z" are the mole fractions of EL, Al and P
respectively and specifically where "x" has a value from about 0.02
to about 0.08 provides an increased selectivity to ethylene and
propylene with a reduction in undesirable C.sub.4s and C.sub.5+. A
preferred catalyst is one which additionally has a predominantly
plate crystal morphology wherein the average smallest crystal
dimension is at least 0.1 micron and has an aspect ratio of less
than or equal to 5
SUMMARY OF THE INVENTION
As stated, this invention relates to a process for converting
methanol to light olefins using a catalyst comprising an ELAPO
molecular sieve. Accordingly, one embodiment of the invention is a
process for converting methanol to light olefins comprising
contacting the methanol with a catalyst at conversion conditions to
provide the olefins, the catalyst comprising a crystalline metallo
aluminophosphate molecular sieve having a chemical composition on
an anhydrous basis expressed by an empirical formula of:
where EL is a metal selected from the group consisting of silicon,
magnesium, zinc, iron, cobalt, nickel, manganese, chromium and
mixtures thereof, "x" is the mole fraction of EL and has a value of
about 0.02 to about 0.08, "y" is the mole fraction of Al and has a
value of at least 0.01, "z" is the mole fraction of P and has a
value of at least 0.01 and x+y+z=1.
In another embodiment, the molecular sieve is characterized in that
it has a crystal morphology wherein the average smallest crystal is
at least 0.1 micron and has an aspect ratio no greater than 5.
These and other objects and embodiments of the invention will
become more apparent after the detailed description of the
invention.
DETAILED DESCRIPTION OF THE INTENTION
An essential feature of the process of the instant invention is an
ELAPO molecular sieve. ELAPOs are molecular sieves which have a
three-dimensional microporous framework structure of AlO.sub.2,
PO.sub.2 and ELO.sub.2 tetrahedral units. Generally the ELAPOs have
the empirical formula:
where EL is a metal selected from the group consisting of silicon,
magnesium, zinc, iron, cobalt, nickel, manganese, chromium and
mixtures thereof, "x" is the mole fraction of EL and has a value of
at least 0.005, "y" is the mole fraction of Al and has a value of
at least 0.01, "z" is the mole fraction of P and has a value of at
least 0.01 and x+y+z=1. When EL is a mixture of metals, "x"
represents the total amount of the metal mixture present. Preferred
metals (EL) are silicon, magnesium and cobalt with silicon being
especially preferred. As will be shown in the examples, when "x"
has a value of about 0.02 to about 0.08 a greater selectivity to
ethylene and propylene with a diminished selectivity to C.sub.4+
components is observed.
The preparation of various ELAPOs are well known in the art and may
be found in U.S. Pat. No. 4,554,143 B1 (FeAPO); U.S. Pat. No.
4,440,871 B1 (SAPO); U.S. Pat. No. 4,853,197 B1 (MAPO, MnAPO,
ZnAPO, COAPO); U.S. Pat. No. 4,793,984 B1 (CAPO), U.S. Pat. No.
4,752,651 B1 and U.S. Pat. No. 4,310,440 B1, all of which are
incorporated by reference. Generally, the ELAPO molecular sieves
are synthesized by hydrothermal crystallization from a reaction
mixture containing reactive sources of EL, aluminum, phosphorus and
a templating agent. Reactive sources of EL are the metal salts such
as the chloride and nitrate salts. When EL is silicon a preferred
source is fumed, colloidal or precipitated silica. Preferred
reactive sources of aluminum and phosphorus are pseudo-boehmite
alumina and phosphoric acid. Preferred templating agents are amines
and quaternary ammonium compounds. An especially preferred
templating agent is tetraethylammonium hydroxide (TEAOH).
The reaction mixture is placed in a sealed pressure vessel,
optionally lined with an inert plastic material such as
polytetrafluoroethylene and heated preferably under autogenous
pressure at a temperature between about 50.degree. C. and
250.degree. C. and preferably between about 100.degree. C. and
200.degree. C. for a time sufficient to produce crystals of the
ELAPO molecular sieve. Typically the time varies from about 1 hour
to about 120 hours and preferably from about 24 hours to about 48
hours. The desired product is recovered by any convenient method
such as centrifugation or filtration.
The ELAPO molecular sieves of this invention have predominantly a
plate crystal morphology. By predominantly is meant greater than
50% of the crystals. Preferably at least 70% of the crystals have a
plate morphology and most preferably at least 90% of the crystals
have a plate morphology. Especially good selectivity (C.sub.2.sup.=
versus C.sub.3.sup.=) is obtained when at least 95% of the crystals
have a plate morphology. By plate morphology is meant that the
crystals have the appearance of rectangular slabs. More
importantly, the aspect ratio is less than or equal to 5. The
aspect ratio is defined as the ratio of the largest crystalline
dimension divided by the smallest crystalline dimension. A
preferred morphology which is encompassed within the definition of
plate is cubic morphology. By cubic is meant not only crystals in
which all the dimensions are the same, but also those in which the
aspect ratio is less than or equal to 2. It is also necessary that
the average smallest crystal dimension be at least 0.1 microns and
preferably at least 0.2 microns.
As is shown in the examples, the morphology of the crystals and the
average smallest crystal dimension is determined by examining the
ELAPO molecular sieve using Scanning Electron Microscopy (SEM) and
measuring the crystals in order to obtain an average value for the
smallest dimension.
Without wishing to be bound by any one particular theory, it
appears that a minimum thickness is required so that the diffusion
path for the desorption of ethylene and propylene is sufficiently
long to allow differentiation of the two molecules. Since ethylene
is a more valuable product, by controlling the crystal dimensions
one can maximize the formation of ethylene. As will be shown in the
examples, when the smallest dimension is less than 0.1, the ratio
of ethylene to propylene (C.sub.2.sup.= /C.sub.3.sup.=) is about
1.2, whereas when the smallest dimension is greater than 0.1
microns, the ratio of C.sub.2.sup.= /C.sub.3.sup.= is about 1.4.
This provides a greater production of ethylene.
The ELAPOs which are synthesized using the process described above
will usually contain some of the organic templating agent in its
pores. In order for the ELAPOs to be active catalysts, the
templating agent in the pores must be removed by heating the ELAPO
powder in an oxygen containing atmosphere at a temperature of about
200.degree. to about 700.degree. C. until the template is removed,
usually a few hours.
As stated above unexpected selectivity is obtained when the metal
(EL) content varies from about 0.02 to about 0.08 mole fraction,
preferably from about 0.02 to about 0.07 and more preferably from
about 0.03 to about 0.068. If EL is more than one metal then the
total concentration of all the metals is between about 0.02 and
0.08 mole fraction. An especially preferred embodiment is one in
which EL is silicon (usually referred to as SAPO). The SAPOs which
can be used in the instant invention are any of those described in
U.S. Pat. No. 4,440,871 B1. Of the specific crystallographic
structures described in the '871 patent, the SAPO-34, i.e.,
structure type 34, is preferred. The SAPO-34 structure is
characterized in that it adsorbs xenon but does not adsorb
isobutane, indicating that it has a pore opening of about 4.2
.ANG..
The ELAPO molecular sieve of this invention may be used alone or
they may be mixed with a binder and formed into shapes such as
extrudates, pills, spheres, etc. Any inorganic oxide well known in
the art may be used as a binder. Examples of the binders which can
be used include alumina, silica, aluminum-phosphate,
silica-alumina, etc. When a binder is used, the amount of ELAPO
which is contained in the final product ranges from 10 to 90 weight
percent and preferably from 30 to 70 weight percent.
The conversion of methanol to light olefins is effected by
contacting the methanol with the ELAPO catalyst at conversion
conditions, thereby forming the desired light olefins. The methanol
can be in the liquid or vapor phase with the vapor phase being
preferred. Contacting the methanol with the ELAPO catalyst can be
done in a continuous mode or a batch mode with a continuous mode
being preferred. The amount of time that the methanol is in contact
with the ELAPO catalyst must be sufficient to convert the methanol
to the desired light olefin products. When the process is carried
out in a batch process, the contact time varies from about 0.001
hr. to about 1 hr. and preferably from about 0.01 hr. to about 1.0
hr. The longer contact times are used at lower temperatures while
shorter times are used at higher temperatures. Further, when the
process is carried out in a continuous mode, the Weight Hourly
Space Velocity (WHSV) based on methanol can vary from about 1
hr.sup.-1 to about 1000 hr.sup.-1 and preferably from about 1
hr.sup.-1 to about 100 hr.sup.-1.
Generally, the process must be carried out at elevated temperatures
in order to form light olefins at a fast enough rate. Thus, the
process should be carried out at a temperature of about 300.degree.
C. to about 600.degree. C., preferably from about 400.degree. C. to
about 550.degree. C. The process may be carried out over a wide
range of pressure including autogenous pressure. Thus, the pressure
can vary from about 0 kPa (0 psig) to about 1724 kPa (250 psig) and
preferably from about 34 kPa (5 psig) to about 345 kPa (50
psig).
Optionally, the methanol feedstock may be diluted with an inert
diluent in order to more efficiently convert the methanol to
olefins. Examples of the diluents which may be used are helium,
argon, nitrogen, carbon monoxide, carbon dioxide, hydrogen, steam,
paraffinic hydrocarbons, e.g., methane, aromatic hydrocarbons,
e.g., benzene, toluene and mixtures thereof. The amount of diluent
used can vary considerably and is usually from about 5 to about 90
mole percent of the feedstock and preferably from about 25 to about
75 mole percent.
The actual configuration of the reaction zone may be any well known
catalyst reaction apparatus known in the art. Thus, a single
reaction zone or a number of zones arranged in series or parallel
may be used. In such reaction zones the methanol feedstock is
flowed through a bed containing the ELAPO catalyst. When multiple
reaction zones are used, one or more ELAPO catalyst may be used in
series to produce the desired product mixture. Instead of a fixed
bed, a dynamic bed system, e.g., fluidized or moving, may be used.
Such a dynamic system would facilitate any regeneration of the
ELAPO catalyst that may be required. If regeneration is required,
the ELAPO catalyst can be continuously introduced as a moving bed
to a regeneration zone where it can be regenerated by means such as
oxidation in an oxygen containing atmosphere to remove carbonaceous
materials.
The following examples are presented in illustration of this
invention and are not intended as undue limitations on the
generally broad scope of the invention as set out in the appended
claims.
EXAMPLE 1
A series of molecular sieves (SAPOs) were prepared by the following
procedure. In a container orthophosphoric acid (85%) was combined
with water. To this there was added a silica sol and a 35 wt. %
aqueous solution of tetraethylammonium hydroxide (TEAOH). Finally,
alumina in the form of pseudo-boehmite along with water and SAPO-34
seed material were added and blended in. The resulting mixtures had
compositions in molar oxide ratios as set forth in Table 1
below.
TABLE 1 Reaction Mixture Compositions For SAPOs Sample Reaction
I.D. Time TEAOH SiO.sub.2 Al.sub.2 O.sub.3 P.sub.2 O.sub.5 H.sub.2
O A 48 1.0 0.10 1.0 1.0 35 B 48 1.0 0.10 1.0 1.0 35 C 48 1.0 0.10
1.0 1.0 45 D 24 1.0 0.10 1.0 1.0 45 E 36 1.0 0.15 1.0 1.0 40 F 48
1.0 0.20 1.0 1.0 45
The mixture was now placed in a steel pressure reactor equipped
with a turbine stirrer. The mixture was now stirred and heated to
100.degree. C. over a 6 hour period, held at 100.degree. C. for 6
hours, then heated to 175.degree. C. over a period of 3 hours and
held there for the reaction time of 24, 36 or 48 hours. Finally,
the reaction mixture was cooled to ambient temperature and the
solid product recovered by centrifugation and washed with water.
All the products were analyzed and found to be SAPO-34 molecular
sieves.
EXAMPLE 2
The catalysts prepared in Example 1 were evaluated for the
conversion of methanol to light olefins in a fixed bed pilot plant.
A 4 gram sample in the form of 20-40 mesh agglomerates was used for
the testing. Before testing, each sample was calcined in air in a
muffle oven at 650.degree. C. for 2 hours and then pretreated in
situ by heating to 400.degree. C. for 1 hour under nitrogen. The
pretreated sample was now contacted with a feed consisting of
methanol and H.sub.2 O in a 1/0.44 molar ratio at 435.degree. C., 5
psig and 2.5 hr.sup.-1 MeOH WHSV. The composition of the effluent
was measured by an on-line GC after 30 minutes on stream to
determine initial conversion and selectivities. Complete conversion
was obtained initially with all catalysts but it fell with time on
stream as the catalysts deactivated. Table 2 presents the
selectivity to ethylene and propylene and the ethylene/propylene
product ratio at the point where conversion was 99% for each
catalyst.
TABLE 2 Effect of Crystal Dimension on Ethylene/Propylene
Production Catalyst Average Smallest Crystal C.sub.2.sup.=
+C.sub.3.sup.= I.D. Dimension (Microns) Morphology Selectivity (%)
C.sub.2.sup.= /C.sub.3.sup.= A 0.07 Thin plates 82.4 1.17 B 0.08
Plates 79.2 1.18 C 0.09 Thin Plates 82.2 1.25 D 0.13 Plates 80.8
1.40 E 0.17 Plates 81.2 1.41 F 0.58 Cubic 78.7 1.48
The average smallest crystallite dimension was determined by
measuring 20 representative crystallites in one or more micrographs
obtained using a Scanning Electron Microscope at 30,000.times.
magnification. The data indicate that when the smallest crystal
dimension is greater than 0.1 micron and the crystal morphology is
plates, a greater amount of ethylene is produced. It is also
observed that when the crystal morphology is cubic and the smallest
dimension is greater than 0.2 microns, one obtains the highest
production of ethylene. Note that when the smallest dimension is
less than 0.1, one obtains poor results (greater propylene
production) even though the crystal morphology is plates.
EXAMPLE 3
A second series of molecular sieves (SAPOs) with various amounts of
silicon were prepared by the following procedure. In a container
orthophosphoric acid (85%) was combined with water. To this there
was added a silica sol and a 35 wt. % aqueous solution of
tetraethylammonium hydroxide (TEAOH) or a mixture of di (n-propyl)
diamine (nPr.sub.2 NH) and TEAOH. Finally, alumina in the form of
pseudo-boehmite along with water and SAPO-34 seed material were
added and blended in. The resulting mixtures had compositions in
molar oxide ratios as set forth in Table 3 below.
TABLE 3 Reaction Mixture Compositions For SAPOs Sample Reaction
I.D. Time TEAOH SiO.sub.2 Al.sub.2 O.sub.3 P.sub.2 O.sub.5 H.sub.2
O G 72 1.0 0.05 1.0 1.0 35 H 24 1.0 0.05 1.0 1.0 35 I 48 1.0 0.10
1.0 1.0 35 J 48 1.0 0.20 1.0 1.0 35 K 48 1.0 0.30 1.0 1.0 35 .sup.
L.sup.1 72 1.0 0.40 1.0 1.0 35 .sup. M.sup.2 17 * 0.60 1.0 1.0 50 *
2.0 n-Pr.sub.2 NH and 0.5 TEAOH .sup.1 no 100.degree. C. hold
.sup.2 no 100.degree. C. hold, reaction temperature 175.degree.
C.
The mixture was now placed in a steel pressure reactor equipped
with a turbine stirrer. The mixture was now stirred and heated to
100.degree. C., held at 100.degree. C. for 6 hours, then heated to
150.degree. C. or 175.degree. C. and held there for the reaction
time. Finally, the reaction mixture was cooled to ambient
temperature and the solid product recovered by centrifugation and
washed with water. All the products were analyzed and found to be
SAPO-34 molecular sieves.
EXAMPLE 4
The catalysts prepared in Example 3 were evaluated for the
conversion of methanol to light olefins in a fixed bed pilot plant.
A 4 gram sample in the form of 20-40 mesh agglomerates was used for
the testing. Before testing, each sample was calcined in air in a
muffle oven at 650.degree. C. for 2 hours and then pre-treated in
situ by heating to 400.degree. C. for 1 hour under nitrogen. The
pretreated sample was now contacted with a feed consisting of
methanol and H.sub.2 O in a 1/0.44 molar ratio at 400.degree. C., 5
psig and 1 hr.sup.-1 methanol WHSV. The composition of the effluent
was measured by an on-line GC after 30 minutes on stream to
determine initial conversion and selectivities. Complete conversion
was obtained initially with all catalysts but it fell with time on
stream as the catalysts deactivated. Table 4 presents the
selectivity to ethylene and propylene and the ethylene/propylene
product ratio at the point where conversion was 99% for each
catalyst.
TABLE 4 Effect of Silicon Content on Olefin Production Catalyst
C.sub.2.sup.= + C.sub.3.sup.= C.sub.4+ Selectivity Coke I.D. Si
(%)* Selectivity (%) C.sub.2.sup.= /C.sub.3.sup.= wt. % G 1.6 81.3
15.8 1.13 15.2 H 1.7 80.9 15.9 1.12 16.0 I 3.2 82.5 12.9 1.30 19.0
J 5.2 83.7 12.1 1.36 21.6 K 6.7 84.8 9.6 1.23 19.4 L 9.5 78.8 16.9
0.96 20.4 M 14.0 73.0 22.1 0.82 13.4 *% of T atoms
The results in Table 4 show that selectivity to ethylene and
propylene increase in the silicon range of about 2% to about 8%
while production of C.sub.4+ byproducts decreases within the same
range. It is also observed that the C.sub.2.sup.= +C.sub.3.sup.=
selectivity increases more between 2% and 7% silicon and the most
between 3% and 6.8% silicon.
* * * * *